Resistors and compositions therefor

ABSTRACT

Powder compositions for producing high resistivity resistors capable of withstanding high voltage surges without large changes in resistivity, said compositions comprising finely divided pyrochlore-related oxides, lead glasses and metal titanates. Alternately to comprising titanates, the compositions may comprise metal titanate precursors such as crystallizable glasses capable of forming metal titanates upon being heated or titanium oxide plus a glass which react to form metal titanates.

BACKGROUND OF THE INVENTION

This invention relates to resistors, and more particularly, to filmresistors capable of operating at high voltage, as well as compositionsfor making same.

Pyrochlore is a mineral of varying composition generally expressed as(Na,Ca)₂ (Nb,Ti)₂ (O,F)₇, but which approaches the simpler formulationNaCaNb₂ O₆ F. The structure of the mineral, established bycharacteristic X-ray reflections, has a cubic unit cell with dimensionsof about 10.4 Angstroms and contains eight formula units of approximatecomposition A₂ B₂ X₆₋₇. The term pyrochlore is used interchangeablyherein with the term pyrochlore-related oxide to mean oxides of thepyrochlore structure with the approximate formula A₂ B₂ O₆₋₇. Compoundsof the pyrochlore-related (cubic) crystal structure are known to beuseful as resistors. See, for example, Schubert U.S. Pat. No. 3,560,410,issued Feb. 2, 1971; Hoffman U.S. Pat. No. 3,553,109, issued Jan. 5,1971; Bouchard U.S. Pat. No. 3,583,931, issued June 8, 1971; PopowichU.S. Pat. No. 3,630,969, issued Dec. 28, 1971; Bouchard U.S. Pat. No.3,681,262, issued Aug. 1, 1972; and Bouchard U.S. Pat. No. 3,775,347,issued Nov. 27, 1973; each of which is incorporated by reference herein.

Such pyrochlore-based resistors have often been found to havedeficiencies when compounded to achieve high resistivities. The highvoltage handling capability of film resistors is important, since incertain demanding high voltage uses a resistor may operate at a voltagestress in the range 1000-3000 volts/inch (40-120 volts/mm), and may beexposed to brief (less than one second duration) voltage surges up to 30kilovolts/inch. As a result of such a voltage surge, most resistorsexhibit a permanent change in resistance of up to 50% of their pre-surgelower operating voltage resistance. Resistors are needed which canundergo high voltage surges without undergoing such large changes inresistivity.

The resistivity of presently available high resistivity resistors isnormally quite dependent on the concentration of the conductive phase.Therefore, resistor compositions less dependent upon variations inconcentration of the conductive phase are needed.

Thus, improved resistor compositions and resistors are needed where highresistivity (1 to 10 megohm per square) are desired, for example, inhigh voltage applications such as voltage divider networks, focuspotentiometers, and other electrical networks.

SUMMARY OF THE INVENTION

This invention is film resistors adherent to a dielectric substrate. Theresistor is adherent to the substrate by virtue of having been printedthereon using typical screen of stencil techniques, followed by firingto sinter or coalesce the deposited inorganic powders to produce acoherent, electrically continuous pattern on the substrate. Theresistors comprise a conductive phase of particles of (1)pyrochlore-related oxides having the general formula A₂ B₂ O₆₋₇ andmetal titanates; each of these types of crystalline particles aredispersed in a matrix of lead-containing glass. The glass contains atleast 5 weight percent lead oxide dissolved therein. The resistorscomprise about 5-15 weight percent of said metal titanate and preferably10-50 weight percent of pyrochlore-related oxide, the remainder of theresistor being the aforementioned lead oxide containing glass.

The metal titanate preferably comprises a multivalent cation in additionto a titanium/oxygen titanate anion. Preferred titanate anions include(TiO₃)²⁻. Preferred pyrochlores are lead ruthenate, bismuth ruthenateand lead iridate. It is preferred that the metal titanate comprisebarium titanate, lead titanate and/or lead zirconate titanate.

Also a part of this invention are powder compositions useful for formingsuch resistors on dielectric substrates using thick-film techniques. Thepower compositions comprise the aforementioned pyrochlore-related oxidesand one or more of the following titanium materials:

1. a metal titanate and a glass comprising at least 10 weight percentPbO dissolved therein, .Iadd.and .Iaddend.

2. .[.one or more glasses at least one of which comprises at least 5weight percent titanium dioxide dissolved therein and a metal oxide andis capable of crystallization to form a metal titanate upon being heatedand 3..]. titanium oxide and a glass comprising at least 10 weightpercent PbO dissolved therein.

In titanium materials (1) and .[.(3).]. .Iadd.(2).Iaddend., the glasspreferably comprises at least 50% by weight PbO dissolved therein. .[.Intitanium material (2) the glass preferably comprises 50-70% PbO, 5-15%TiO₂, 15-35% SiO₂ and 0-15% Al₂ O₃..]. In titanium material .[.(3).]..Iadd.(2) .Iaddend.the preferred titanium oxide is titanium dioxide,although oxygen deficient titanium oxides may also be employed.

In titanium materials (1) and (3), the glass preferably comprises atleast 50% by weight PbO dissolved therein. In titanium material (2) theglass preferably comprises 50-70% PbO, 5-15% TiO₂, 15-35% SiO₂ and 0-15%Al₂ O₃. In titanium material (3) the preferred titanium oxide istitanium dioxide, although oxygen deficient titanium oxides may also beemployed.

In these powder compositions there is sufficient titanium material toproduce an amount of metal titanate equal to 5-15 weight percent of thetotal weight of the inorganics present in the composition. Also in thepowder compositions the amount of pyrochlore-related oxide is preferably10-50 weight percent. The preferred pyrochlore-related oxides are leadruthenate, bismuth ruthenate, and lead iridate. It is preferred in thepowder compositions that the metal titanate be of a multivalent cation,that is, a cation having a positive valence of at least +2. In titaniummaterial (2) .[.it is preferred that the metal oxide capable of forminga metal titanate also be multivalent; in titanium material (3),.]. it ispreferred that the glass comprise a large amounts of PbO and/or othermultivalent cations.

The powder cmpositions of this invention may optionally be dispersed inan inert vehicle such as is typically used in thick-film techniques; theinert vehicle is typically a liquid.

DETAILED DESCRIPTION OF THE INVENTION

The resistors of this invention have enhanced ability to withstand highvoltage; also the resistivity of resistors of this invention is lesssensitive to variations in concentration of the conductive phase. Theconductive phase in the resistors of this invention is one or morepyrochlore-related oxides. Particles of the conductive phase aredispersed in a glassy lead-containing matrix, along with particles of ametal titanate. The metal titanate is, as shown by the examples,responsible for the improved performance of the resistors of thisinvention.

The metal titanate serves to (1) raise the resistivity of the resistorrelative to compositions having the same amount of conductive phase(pyrochlore) and (2) to enhance the voltage withstanding capacity of theresistor. It is thought that the increase in resistivity is likelycaused by additional segregation of the conductive phase in the presenceof the titanate. The metal titanate detracts from the role of the glassas a liquid phase sintering aid for the pyrochlore, with conductivephase segregation the result. It is thought that the metaltitanate-based dielectrics improve voltage withstanding capabilitybecause of their ability to store the electrical energy in the form of apolarization, instead of expenditure of that energy in the form ofelectric currents which cause permanent changes in the microstructureand thus permanent changes in resistance.

The metal titanates in the resistors of this invention, and in thepowder compositions in one of the embodiments of this invention, arecrystalline materials and comprise a metal cation and a titanate anion.The titanates may be represented by the general formula [M]_(a) [Ti_(x)O_(y) ]_(b) where the total positive charge of the cation(s) M and thetotal negative charge of the anions [Ti_(x) O_(y) ] are equal. Thus,where M is univalent, the titanate may be (M⁺¹)₂ TiO₃ ; where M isdivalent the titanate may be M⁺² TiO₃ ; where M is trivalent thetitanate may be (M⁺³)₂ (TiO₃)₃, etc.

The titanate anion may be (TiO₃)²⁻ as in ATiO₃ materials of the ilmenitestructure where A is Fe⁺², Ni⁺², Mn⁺², Mg⁺² ; it may be (TiO₄)²⁻ as inA₂ TiO₄ materials of the spinel structure where A is Ni⁺², Mn⁺², etc.;it may be (TiO₃)²⁻ as in the perovskite structure where A is Ca⁺², Ba⁺²,Sr⁺², Pb⁺² ; it may be (Ti₂ O₇)⁶⁻ as in the distorted cubic structuresA₂ Ti₂ O₇ where A is Bi⁺³ ; it may be (TiO₄)⁴⁻ of the K₂ SO₄ crystallinestructure A₂ TiO₄ where A is Ca⁺², Ba⁺². The above list of metaltitanates is illustrative only.

Preferred metal titanates include PbTiO₃, BaTiO₃, CaTiO₃, FeTiO₃,SrTiO₃, and PZT (Pb₁.0 Zr₀.57 T₀.43 O₃), especially as components of thepowder compositions of this invention.

The metal titanates are preferably 5-15% by weight of the resistor, andof the powder composition (unless formed in situ). Generally, at least5% metal titanate is present to achieve significant resistor propertyimprovements. Amounts of metal titanates in excess of 15 weight percent,while improving voltage characteristics, tend to cause high negativetemperature coefficient of resistance, TCR (e.g., greater than 1000p.p.m./°C.). A negative TCR means that the resistance varies negativelywith temperature.

The metal cation in the metal titanates may be any metal cation,including those of Groups I through V, Periodic Table of Elements(Metals Handbook, Am. Soc. Metals, 8th Ed., 1961, Vol. 1, p. 42) This,of course, includes the alkali and alkaline earth cations of Groups Iand II, the transition elements of Groups III and IV, and the heaviermetals of Group V (As, Sb, Ti). The maximum atomic number of the metalsis hence that of bismuth (83). It is preferred that the metals bemultivalent, i.e., more than univalent. Hence, the univalent alkalimetals are not preferred.

The pyrochlore-related oxide (also referred to as pyrochlores herein)include polynary oxides of the formula (M_(x) Bi_(2-x))(M'_(y)Ru_(2-y))O_(7-z), wherein

M is at least one metal selected from the group consisting of yttrium,indium, cadmium, lead and the rare earth metals of atomic number 57-71,inclusive;

M' is at least one metal selected from the group consisting of platinum,titanium, tin, chromium, rhodium, iridium, zirconium, antimony andgermanium;

x is a number in the range 0-2;

y is a number in the range 0-2; and

z is a number in the range 0-1, being at least equal to about x/2 when Mis a divalent metal.

Also included are the pyrochlores disclosed in commonly assignedBouchard and Rogers USSN 326,955, filed Jan. 25, 1973, now U.S. Pat. No.3,896,055, of the formula

    M.sub.x M'.sub.2-x M".sub.2 O.sub.7-z

wherein:

M is at least one of Ag or Cu;

M' is Bi or a mixture of at least one half Bi plus up to one half of oneor more cations from among

a. bivalent Cd or Pb and

b. trivalent Y, Tl, In and rare earth metals of atomic number 57-71,inclusive;

M" is at least one of

a. Ru,

b. Ir, and

c. a mixture of at least three-fourths of at least one of Ru and Ir andup to one-fourth of at least one of Pt, Ti and Rh;

x is in the range 0.10 to 0.60 (preferably 0.10 to 0.5) and

z is in the range 0.10 to 1.0, and is equivalent to the sum ofmonovalent cations M and half of divalent cations in the polynary oxide.

Optimum pyrochlores include Pb₂ Ru₂ O₆, Bi₂ Ru₂ O₇, Pb₂ Ir₂ O₆, and Bi₂Ir₂ O₇.

The glasses used in the powder compositions of the present invention arelead-containing glasses (they comprise at least 10% PbO, preferably50-80% PbO, along with other glass forming oxides such as SiO₂ Al₂ O₃,TiO₂, ZnO, BaO, P₂ O₅, V₂ O₅, etc.).

.[.Where the metal titanate is to be provided in the resistor by in situcrystallization of the glass during firing, a crystallizable TiO₂-containing glass is used in the desired quantities. The glass normallycontains at least 5% TiO₂ dissolved therein, and also a metal oxide.Exemplary of such crystallizable glasses are those of Stookey U.S. Pat.No. 2,920,971, issued Jan. 12, 1960. Useful crystallizable glasses alsoinclude lead titanium silicates and aluminosilicates of.].

.Badd..[.50-70% PbO.]..Baddend.

.Badd..[.5-15% TiO₂ .]..Baddend.

.Badd..[.15-35% SiO₂ .]..Baddend.

.Badd..[.0-15% Al₂ O₃ .]..Baddend.

.[.Optimum crystallizable glasses 60% PbO, 7% TiO₂, 32% SiO₂ and 1% Al₂O₃..].

Where the powder composition .[.contains neither.]. .Iadd.does notcontain .Iaddend.preformed metal titanates .[.nor a crystallizable TiO₂-containing glass,.]. it .[.may comprise.]. .Iadd.comprises .Iaddend.amixture of titanium oxide and a glass which reacts therewith (or firing)to form metal titanates. Such glasses comprise, dissolved therein, atleast 10% PbO, preferably 50-80% PbO, and optionally other preferredmetal oxides such as BaO, Bi₂ O₃, etc. By titanium oxide is meant TiO₂or any of the well-known oxygen deficient titanium oxide such as thosementioned by A. F. Wells in Structural Inorganic Chemistry, Oxford,Clarendon Press, 3rd Edition, 1962, p. 475. TiO₂ is preferred.

The relative amounts of pyrochlore and glass in the resistors andresistor compositions of this invention are selected according togenerally known principles dependent upon the desired resultantproperties. Generally, for these high resistivity resistors the amountof pyrochlore in the resistors and in the resistor compositions (on asolids basis) will be 10-50%, preferably 15-45%. The amount of glass inthe resistors, and in resistor compositions wherein the titanates arenot to be formed in situ, will be the difference between total weight ofpyrochlore (10-50%) and titanate (5-15%) and 100%, or 35-85% glass.

Optimum compositions according to this invention are of 7.3% BaTiO₃,21.7% Pb₂ Ru₂ O₆ and 71% lead aluminosilicate glass.

The resistor (powder) compositions of the present invention may beprinted on any conventional dielectric substrate (e.g., alumina, ceria,etc.) using thick-film techniques. By "thick film" is meant filmsobtained by printing dispersions of powders (usually in an inert liquidvehicle) on a substrate using techniques such as screen and stencilprinting, as opposed to the so-called "thin" films deposited byevaporation or sputtering. Thick-film technology is discussed generallyin Handbook of Materials and Processes for Electronics, C. A. Harper,Editor, McGraw-Hill, New York, 1970, Chapter 11.

The powders are sufficiently finely divided to be used in conventionalscreen or stencil printing operations and to facilitate sintering. Thecompositions are prepared from the solids and vehicles by mechanicalmixing and printed as a film on ceramic dielectric substrates in theconventional manner. Any inert liquid may be used as the vehicle. Wateror any one of various organic liquids, with or without thickening and/orstabilizing agents and/or other common additives, may be used as thevehicle. Exemplary of the organic liquids which can be used are thealiphatic alcohols; esters of such alcohols, for example, the acetatesand propionates; terpenes such as pine oil, terpineol and the like;solutions of resins such as the polymethacrylates of lower alcohols, orsolutions of ethylcellulose, in solvents such as pine oil and themonobutyl ether of ethylene glycol monoacetate. The vehicle may containor be composed of volatile liquids to promote fast setting afterapplication to the substrate.

The ratio of inert liquid vehicle to solids in the dispersions may varyconsiderably and depends upon the manner in which the dispersion is tobe applied and the kind of vehicle used. Generally, from 0.2 to 20 partsby weight of solids per part by weight of vehicle will be used toproduce a dispersion of the desired consistency. Preferred dispersionscontain 20-70% vehicle.

The printed pattern is normally dried at 100°-150° C.to remove solvent.Firing or sintering of the powder compositions of the present inventionnormally occurs at temperatures in the range 750°-950° C., for 5 minutesto 2 hours, depending on the particular compositions employed and thedesired degree of sintering, as will be known to those skilled in theart. Generally, shorter firing times may be employed at highertemperatures. As one skilled in the art knows when crystallizableglasses are used, heating should be sufficiently long to permitnucleation and crystal formation.

EXAMPLES

The following examples are presented to illustrate the invention. In theexamples and elsewhere in the specification and claims all parts,percentages, and ratios are by weight, unless otherwise stated.

The high voltage handling capability of film resistors was evaluated bysubjecting the resistors to stress (stressed) at voltage gradients up to50 kilovolts/inch (127 kv/cm) for 15 seconds. Resistance before stress(Ro) was compared with resistance after stress (R_(ref)), each measuredat low stress (typically 500 volts/mm.) and the percent permanent changein resistance was defined as ##EQU1##

The resistors were prepared as follows. A dispersion or paste of theseven parts of the solids indicated below in three parts an inert liquidvehicle (1/9 ethylcellulose/terpineol) was prepared by conventionalroll-milling techniques. The paste was printed on Alsimag 614 aluminasubstrates bearing prefired Pd/Ag (1/2.5) electrode terminations, usinga 200-mesh screen to print 25 mm square patterns. The pattern was driedat 150° C. in an air oven for 15 minutes (to a thickness of about 25microns) and then fired in a belt furnace to a maximum temperature ofabout 850° C. (about 8 minutes at peak); total furnace residence timewas about 45-60 minutes. The dried print about 17 microns thick.

The glasses used in the Examples are designated A, B and C therein, andare identified in Table I.

                  TABLE 1                                                         ______________________________________                                        GLASSES USED IN EXAMPLES (WT. %)                                              Glass A        Glass B      Glass C                                           ______________________________________                                        65.0% PbO      32.0% PbO    60.0% PbO                                         34.0% SiO.sub. 2                                                                             27.0% SiO.sub.2                                                                            32.0% SiO.sub.2                                   --1.0% Al.sub.2 O.sub.3                                                                      11.0% Al.sub.2 O.sub.3                                                                      1.0% Al.sub.2 O.sub.3                                           12.0% TiO.sub.2                                                                             7.0% TiO.sub.2                                                  10.0% ZnO                                                                      8.0% BaO                                                      ______________________________________                                    

The inorganic materials used herein, and their relative proportions, areset forth in Tables II-V. The powders were each finely divided (byconventional milling techniques), the surface areas being forpyrochlore-related oxides, 9.0-14.0 m.² /g., for titanate powders4.0-5.0 m.² /g., for glasses 6.0-8.0 m.² /g., and for TiO₂ 9 m.² /g.

EXAMPLES 1-3; SHOWINGS A-C (TABLE II)

In Examples 1-3 and Showings A and C (Table II) the conductive phase andglass were the same. In examples 1-3, barium titanate (BaTiO₃) wereadded. Each was stressed, as indicated in Table II, at 700 or 1000volts/mm. The Examples comprising barium titanate were found to exhibita percent permanent change in resistivity which was about an order ofmagnitude less than that observed where barium titanate was absent.

To emphasize that not any crystalline phase will function to reducechange in resistivity, a crystallizing glass which forms crystals otherthan titanate was employed in Showing B. the major crystalline phaseformed in the glass after firing was BaAl₂ Si₂ O₈ ; a minor amount(probably much less than 3% of the total composition) of Al₂ TiO₅ mayhave been formed. The percent permanent change in resistivity wassimilar to that of Showings A and C.

EXAMPLES 4-9; SHOWING D (TABLE III)

Resistors of higher sheet resistivity than those of Table II wereexamined here. The same conductive phase (lead ruthenate) was usedthroughout, but the titanate additive was varied; the latter wasprovided to the fired resistor by including a titanate powder to theprinting paste (barium titanate at various levels in Examples 4 and 5;lead titanate in Example 6); by adding lead titanate zirconate powder tothe paste (Example 7); by adding TiO₂ powder to paste, which reactedwith the glass to form a titanate on firing (Example 8); or by using aglass which partially crystallizes to lead titanate on firing (Example9).

Showing D used a composition not of this invention, lead ruthenate andthe noncrystallizing glass of Examples 4-8, but no titanates ortitanate-formers; however, the sheet resistivity was similar to that ofExamples 4-9. Table III shows compositions and results.

BaTiO₃ additions of 7.3% and 14.3% (Examples 4 and 5, respectively) tocompositions containing Pb₂ Ru₂ O₆ and lead aluminosilicate glass resultin nearly two order of magnitude decrease of the permanent resistancechange, after voltage stressing at 1000 v/mm, over Comparative Showing Dwithout BaTiO₃.

Examples 6 and 7 emphasize that improved voltage properties may also beobtained with additions of other titanate-based dielectric, namelyPbTiO₃ and PZT.

In Example 8, TiO₂ was added to a Pb₂ Ru₂ O₆ /lead aluminosilicatecomposition. X-ray diffraction data for the fired resistors revealedthat the TiO₂ had combined during firing with the lead-based glass toform PbTiO₃.

                                      TABLE II                                    __________________________________________________________________________                                         V                                                                R (Sheet                                                                           (Voltage                                                                              ΔR.sub.perm.                       Conductive Phase                                                                              Glass Phase                                                                           BaTiO.sub.2                                                                        Resistivity)                                                                          Stress)                                                                              (% Perm. Resist.                  (wt. %)         (wt. %) (wt. %)                                                                            (kohm/square)                                                                         (volts/mm.)                                                                          Change)                           __________________________________________________________________________    Example 1                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (35.2)                                                        Type A (57.7)                                                                         7.1  110      700    1.5                              Example 2                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (28.6)                                                        Type A (64.3)                                                                         7.1  350     1000    2.0                              Example 3                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (24.3)                                                        Type A (68.6)                                                                         7.1  875     1000    0.6                              Showing A                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (21.0)                                                        Type A (79.0)                                                                         --   123      700   14.0                              Showing B                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (23.6)                                                        Type B (76.4)                                                                         --   102      700   12.0                              Showing C                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (19.5)                                                        Type A (80.5)                                                                         0.0  523     1000   12.0                              __________________________________________________________________________

The voltage properties were superior to those of Comparative Showing D.

In Example 9, PbTiO₃ was introduced into the final resistor compositionusing a crystallizable glass. Again the permanent resistance changeafter voltage stressing is significantly smaller than for ComparativeShowing D.

                                      TABLE III                                   __________________________________________________________________________                                           V                                                                    R (Sheet (Voltage                                                                            ΔR.sub.perm                Conductive Phase                                                                              Glass Phase                                                                          Additive                                                                             Resistivity)                                                                           Stress)                                                                             (% Perm. Resist.                 (wt. %)         (wt. %)                                                                              (wt. %)                                                                              (Megohm/square)                                                                        (volts/mm)                                                                          Change)                          __________________________________________________________________________    Showing D                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (17.4)                                                        Type A (82.6)                                                                         --    1.00     1000  25.0                             Example 4                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (21.7)                                                        Type A (71.0)                                                                        BaTiO.sub.3 (7.3)                                                                    1.48     "     0.3                              Example 5                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (21.4)                                                        Type A (64.3)                                                                        BaTiO.sub.3 (14.3)                                                                   2.58     "     0.3                              Example 6                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (29.0)                                                        Type A (63.8)                                                                        PbTiO.sub.3 (7.2)                                                                    1.70     "     1.7                              Example 7                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (29.0)                                                        Type A (63.8)                                                                        PZT* (7.2)                                                                           1.17     "     3.0                              Example 8                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (29.0)                                                        Type A (63.8)                                                                        TiO.sub.2 (7.2)                                                                      1.06     "     0.9                              Example 9                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (16.1)                                                        Type C (83.9)                                                                         --    2.19     "     1.0                              __________________________________________________________________________     *PZT or lead zirconate titanate has the approximate composition Pb.sub.1.     Zr.sub.9.97 Ti.sub. 9.42 O.sub.3.                                        

                                      TABLE IV                                    __________________________________________________________________________                                           V                                                                   R(Sheet   (Voltage                                                                            ΔR.sub.perm.               Conductive Phase                                                                              Glass Phase                                                                           BaTiO.sub.3                                                                        Resistivity)                                                                            Stress)                                                                             (% Perm. Resist.                 (wt. %)         (wt. %) (wt. %)                                                                            (megohm/square)                                                                         (volt/mm)                                                                           Change)                          __________________________________________________________________________    Showing E                                                                           Bi.sub.2 Ru.sub.2 O.sub.2 (21.0)                                                        Type A (79.0)                                                                         --   1.67      1000  38.0                             Example 10                                                                          Bi.sub.2 Ru.sub.2 O.sub.7 (29.4)                                                        Type A (63.2)                                                                         7.4  1.84      "      0.8                             Showing F                                                                           Pb.sub.2 Ir.sub.2 O.sub.6 (36.2)                                                        Type A (63.8)                                                                         --   1.55      200   55.0                             Example 11                                                                          Pb.sub.2 Ir.sub.2 O.sub.6 (41.1)                                                        Type A (53.4)                                                                         5.5  10.92     200    0.4                             __________________________________________________________________________

EXAMPLES 10 and 11; SHOWINGS E AND F (TABLE IV)

The effectiveness of titanates in reducing permanent change inresistivity after high voltage stress using other pyrochlore-relatedoxides is illustrated by these Examples and Showings. Compositions anddata are set forth in Table IV.

EXAMPLES 12, 13, 14, and 15; SHOWINGS G AND H (TABLE V)

Showings G and H emphasize the major impediment to easy manufacture ofhigh resistivity compositions. Only a very small difference in theweight percent conductive phase (1.3%) causes a change in resistance ofone order of magnitude (1 to 10 megohms per square). This property isresponsible for lack of reproducibility in the manufacture of highresistivity compositions.

In Examples 12 and 13, additions of BaTiO₃ show that a much greaterdifference (9.8%) in the conductive phase concentration is possible forsheet resistivities in that range. Hence, barium titanate additions makethe high resistivity compositions much less sensitive to pyrochloreconcentration.

In Examples 14 and 15, where a crystallizable glass is used, theconductive phase increment is 8.7% for 1 megohm/square and 10megohms/square sheet resistivities, again a substantial improvement overthat in Showings G and H.

                                      TABLE V                                     __________________________________________________________________________                                 R (Sheet                                         Conductive Phase                                                                              Glass Phase                                                                           BaTiO.sub.3                                                                        Resistivity)                                                                            Change in Wt. %                        (wt. %)         (wt. %) (wt. %)                                                                            (megohm/square)                                                                         Conductive Phase                       __________________________________________________________________________    Showing                                                                             Pb.sub.2 Ru.sub.2 O.sub.6 (18.4)                                                        Type A (81.6)                                                                         --    1                                                                                      1.3                                    Showing H                                                                           Pb.sub.2 Ru.sub.2 O.sub.6 (17.1)                                                        Type A (82.9)                                                                         --   10                                               Example 12                                                                          Pb.sub.2 Ru.sub.2 O.sub.6 (41.2)                                                        Type A (51.4)                                                                         7.4  1                                                                                       9.8                                    Example 13                                                                          Pb.sub.2 Ru.sub.2 O.sub.6 (31.4)                                                        Type A (61.2)                                                                         7.4  10                                               Example 14                                                                          Pb.sub.2 Ru.sub.2 O.sub.6 (42.0)                                                        Type C (58.0)                                                                         --   1                                                                                       8.7                                    Example 15                                                                          Pb.sub.2 Ru.sub.2 O.sub.6 (33.3)                                                        Type C (66.7)                                                                         --   10                                               __________________________________________________________________________

Showings J, K, and L

The unique effect of titanates in enhancing voltage-withstanding abilityis illustrated by these Showings, which use bismuth stannate, (Bi)₂(SnO₃)₃ ; lead zirconate, PbZrO₃ ; and lead niobate, PbNb₂ O₆. Thecomposition and data are:

Showing J

Pb₂ Ru₂ O₆, 29.0%

Type A Glass, 63.8%

Bi₂ (SnO₃)₃, 7.2%

R, 0.94 megohm/square

Voltage stress, 1000 volts/mm

ΔR_(perm)., 14.0%

Showing K

Pb₂ Ru₂ O₆, 29.4%

Type A Glass, 63.2%

PbZrO₃, 7.4%

R, 187 Kohms/square

Voltage stress, 700 volts/mm

ΔR_(perm)., 23%

Showing L

Pb₂ Ru₂ O₆, 29.0%

Type A Glass, 63.8%

PbNb₂ O₆, 7.2%

R, 200 Kohms/square

Voltage stress, 700 volts/mm

ΔR_(perm)., 23%

I claim:
 1. A film resistor adherent to a dielectric substrate whereinthe resistor comprises a conductive phase of crystalline particles of(1) pyrochlore-related oxides and (2) metal titanates, each dispersed ina matrix of a lead containing glass, said .[.pyrochlore-related oxidesbeing selected from among those of formula

    (M.sub.x Bi.sub.2-x)(M'.sub.y Ru.sub.z-y)O.sub.7-z,

wherein M is at least one metal selected from the group consisting ofyttrium, indium, cadmium, lead, and the rare earth metals of atomicnumber 57-71, inclusive; M' is at least one metal selected from thegroup consisting of platinum, titanium, tin, chromium, rhodium, iridium,zirconium, antimony, and germanium; x is a number in the range 0-2; y isa number in the range 0-2; and z is a number in the range 0-1, being atleast equal to about x/2 when M is a divalent metal; those of theformula

    M.sub.x M'.sub.2-x M".sub.2 O.sub.7-z,

wherein M is at leat one of Ag or Cu; M' is Bi or a mixture of at leastone half Bi plus up to one half of one or more cations from amonga.bivalent Cd or Pb and b. trivalent Y, Tl, In, and rare earth metals ofatomic number 57-71, inclusive; M" is at least one ofa. Ru, b. Ir, andc. a mixture of at least three-fourths of at least one of Ru and Ir andup to one-fourth of at least one of Pt, Ti, and Rh; x is in the range0.10 to 0.60, and z is in the range 0.10 to 1.0, and is equivalent tothe sum of monovalent cations M and half of divalent cations in saidformula; and mixtures thereof.]. .Iadd.resistor being a sinteredcomposition of claim 19.Iaddend.. .[.
 2. A resistor according to claim 1comprising 5-15 weight percent of said metal titanate..]. .[.3. Aresistor according to claim 1 wherein said glass contains at least 5weight percent PbO dissolved therein..]. .[.4. A resistor according toclaim 2 wherein said glass contains at least 5 weight percent PbOdissolved therein..]. .[.5. A film resistor according to claim 1 whereinsaid metal titanate comprises a multivalent cation..]. .[.6. A filmresistor according to claim 2 wherein said metal titanate comprises amultivalent cation..]. .[.7. A film resistor according to claim 1 wherethe anion in said titanate is (TiO₃)²⁻..]. .[.8. A film resistoraccording to claim 2 where the anion in said titanate is (TiO₃)²⁻..]..[.9. A film resistor according to claim 5 where the anion in saidtitanate is (TiO₃)²⁻..]. .[.10. A film resistor according to claim 6where the anion in said titanate is (TiO₃)²⁻..]. .[.11. A film resistoraccording to claim 1 comprising 10-50 weight percent pyrochlore-relatedoxide..]. .[.12. A film resistor according to claim 2 comprising 10-50weight percent pyrochlore-related oxide..]. .[.13. A resistor accordingto claim 1 wherein the pyrochlore-related oxide is Pb₂ Ru₂ O₆..]. .[.14.A film resistor according to claim 1 wherein said pyrochlore-relatedoxide is Bi₂ Ru₂ O₇..]. .[.15. A film resistor according to claim 1wherein said pyrochlore-related oxide is Pb₂ Ir₂ O₆..]. .[.16. Aresistor according to claim 1 wherein said titanate comprises bariumtitanate..]. .[.17. A resistor according to claim 1 wherein saidtitanate comprises lead titanate..]. .[.18. A resistor according toclaim 1 wherein said titanate comprises lead zirconate titanate..]. 19.A powder composition useful for forming film resistors on a dielectricsubstrate, the powder comprising pyrochlore-related oxides and atitanium material selected from the class consisting of1. a metaltitanate and a glass comprising at least 10 weight percent PbO dissolvedtherein, .Iadd.and .Iaddend.
 2. .[.one or more glasses at least one ofwhich comprises at least 5 weight percent titanium dioxide dissolvedtherein and a metal oxide and is capable of crystallization to form ametal titanate upon being heated and.]..[.3..].titanium oxide and aglass comprising at least 10 weight percent PbO dissolved therein,saidpyrochlore-related oxides being selected from among those of the formula

    (M.sub.x Bi.sub.2-x)(M'.sub.y Ru.sub.2-y)O.sub.7-z,

wherein M is at least one metal selected from the group consisting ofyttrium, indium, cadmium, lead, and the rare earth metals of atomicnumber 57-71, inclusive; M' is at least one metal selected from thegroup consisting of platinum, titanium, tin, chromium, rhodium, iridium,zirconium, antimony, and germanium, x is a number in the range 0-2; y isa number in the range 0-2; and z is a number in the range 0-1, being atleast equal to about x/2 when M is a divalent metal; those of theformula M_(x) M'_(2-x) M"₂ O₇₋₇, wherein M is at least one of Ag or Cu;M' is Bi or a mixture of at least one half Bi plus up to one half of oneor more cations from amonga. bivalent Cd or Pb and b. trivalent Y, Tl,In, and rare earth metals of atomic number 57-71, inclusive; M" is atleast one ofa. Ru, b. Ir, and c. a mixture of at least three-fourths ofat least one of Ru and Ir and up to one-fourth of at least one of Pt,Ti, and Rh; x is in the range 0.10 to 0.60, and z is in the range 0.10to 1.0, and is equivalent to the sum of monovalent cations M and half ofdivalent cations in said formula; and mixtures thereof.
 20. Acomposition according to claim 19 comprising titanium material (1). 21.A composition according to claim 20 wherein said glass comprises atleast 50% PbO dissolved therein.
 22. A composition according to claim 19comprising titanium material (2). .[.23. A composition according toclaim 22 wherein said glass comprises 50-70% PbO, 5-15% TiO₂, 15-35%SiO₂ and 0-15% Al₂ O₃..]. .[.24. A composition according to claim 19comprising titanium material (3)..]. A composition according to claim.[.24.]. .Iadd.22 .Iaddend.wherein said glass comprises at least 50% PbOdissolved therein.
 26. A composition according to claim .[.24.]..Iadd.22 .Iaddend.wherein said titanium oxide is TiO₂.
 27. A compositionaccording to claim 25 wherein said titanium oxide is TiO₂.
 28. A powdercomposition according to claim 20 comprising sufficient titaniummaterial to produce an amount of metal titanate equal to 5-15 weightpercent of the total composition weight. A powder composition accordingto claim 22 comprising sufficient titanium material to produce an amountof metal titanate equal to 5-15 weight percent of the total compositionweight.
 30. A powder composition according to claim .[.24.]. .Iadd.27.Iaddend.comprising sufficient titanium material to produce an amount ofmetal titanate equal to 5-15 weight percent of the total compositionweight.
 31. A powder composition according to claim 19 wherein saidpyrochlore-related oxide is Pb₂ Ru₂ O₆.
 32. A powder compositionaccording to claim 19 wherein said pyrochlore-related oxide is Bi₂ Ru₂O₇.
 33. A powder composition according to claim 19 wherein saidpyrochlore-related oxide is Pb₂ Ir₂ O₆.
 34. A powder compositionaccording to claim 20 wherein said pyrochlore-related oxide is Pb₂ Ru₂O₆.
 35. A powder composition according to claim 20 wherein saidpyrochlore-related oxide is Bi₂ Ru₂ O₇.
 36. A powder compositionaccording to claim 20 wherein said pyrochlore-related oxide is Pb₂ Ir₂O₆.
 37. A powder composition according to claim 22 wherein saidpyrochlore-related oxide is Pb₂ Ru₂ O₆.
 38. A powder compositionaccording to claim 22 wherein said pyrochlore-related oxide is Bi₂ Ru₂O₇.
 39. A powder composition according to claim 22 wherein saidpyrochlore-related oxide is Pb₂ Ir₂ O₆.
 40. A powder compositionaccording to claim .[.24.]. .Iadd.27 .Iaddend.wherein saidpyrochlore-related oxide is Pb₂ Ru₂ O₆.
 41. A powder compositionaccording to claim .[.24.]. .Iadd.27 .Iaddend.wherein saidpyrochlore-related oxide is Bi₂ Ru₂ O₇.
 42. A powder compositionaccording to claim .[.24.]. .Iadd.27 .Iaddend.wherein saidpyrochlore-related oxide is Pb₂ Ir₂ O₆.
 43. A composition according toclaim 20 wherein the metal in said metal titanate is multivalent.
 44. Acomposition according to claim 22 wherein the metal in said metal oxideis multivalent.
 45. A composition according to claim 19 comprising 10-50weight percent pyrochlore-related oxide.
 46. A composition according toclaim 20 comprising 10-50 weight percent pyrochlore-related oxide.
 47. Acomposition according to claim 22 comprising 10-50 weight percentpyrochlore-related oxide.
 48. A composition according to claim .[.24.]..Iadd.27 .Iaddend.comprising 10-50 weight percent pyrochlore-relatedoxide.
 49. The composition of claim 19 dispersed in an inert liquidvehicle.
 50. The composition of claim 20 dispersed in an inert liquidvehicle.
 51. The composition of claim 22 dispersed in an inert liquidvehicle.
 52. The composition of claim .[.24.]. .Iadd.27.Iaddend.dispersed in an inert liquid vehicle.
 53. The composition ofclaim 45 dispersed in an inert liquid vehicle. .Iadd.54. A film resistoradherent to a dielectric substrate wherein the resistor comprises aconductive phase of crystalline particles of (1) pyrochlore-relatedoxides and (2) metal titanates, each dispersed in a matrix of a leadcontaining glass, said resistor being a sintered composition of claim20. .Iaddend. .Iadd.55. A film resistor adherent to a dielectricsubstrate wherein the resistor comprises a conductive phase ofcrystalline particles of (1) pyrochlore-related oxides and (2) metaltitanates, each dispersed in a matrix of a lead containing glass, saidresistor being a sintered composition of claim
 21. .Iaddend. .Iadd.56. Afilm resistor adherent to a dielectric substrate wherein the resistorcomprises a conductive phase of crystalline particles of (1)pyrochlore-related oxides and (2) metal titanates, each dispersed in amatrix of a lead containing glass, said resistor being a sinteredcomposition of claim
 22. .Iaddend. .Iadd.57. A film resistor adherent toa dielectric substrate wherein the resistor comprises a conductive phaseof crystalline particles of (1) pyrochlore-related oxides and (2) metaltitanates, each dispersed in a matrix of a lead containing glass, saidresistor being a sintered composition of claim
 25. .Iaddend. .Iadd.58. Afilm resistor adherent to a dielectric substrate wherein the resistorcomprises a conductive phase of crystalline particles of (1)pyrochlore-related oxides and (2) metal titanates, each dispersed in amatrix of a lead containing glass, said resistor being a sinteredcomposition of claim
 26. .Iaddend. .Iadd.59. A film resistor adherent toa dielectric substrate wherein the resistor comprises a conductive phaseof crystalline particles of (1) pyrochlore-related oxides and (2) metaltitanates, each dispersed in a matrix of a lead containing glass, saidresistor being a sintered composition of claim
 27. .Iaddend. .Iadd.60. Afilm resistor adherent to a dielectric substrate wherein the resistorcomprises a conductive phase of crystalline particles of (1)pyrochlore-related oxides and (2) metal titanates, each dispersed in amatrix of a lead containing glass, said resistor being a sinteredcomposition of claim
 28. .Iaddend. .Iadd.61. A film resistor adherent toa dielectric substrate wherein the resistor comprises a conductive phaseof crystalline particles of (1) pyrochlore-related oxides and (2) metaltitanates, each dispersed in a matrix of a lead containing glass, saidresistor being a sintered composition of claim
 29. .Iaddend. .Iadd.62. Afilm resistor adherent to a dielectric substrate wherein the resistorcomprises a conductive phase of crystalline particles of (1)pyrochlore-related oxides and (2) metal titanates, each dispersed in amatrix of a lead containing glass, said resistor being a sinteredcomposition of claim
 30. .Iaddend. .Iadd.63. A film resistor adherent toa dielectric substrate wherein the resistor comprises a conductive phaseof crystalline particles of (1) pyrochlore-related oxides and (2) metaltitanates, each dispersed in a matrix of a lead containing glass, saidresistor being a sintered composition of claim
 31. .Iaddend. .Iadd.64. Afilm resistor adherent to a dielectric substrate wherein the resistorcomprises a conductive phase of crystalline particles of (1)pyrochlore-related oxides and (2) metal titanates, each dispersed in amatrix of a lead containing glass, said resistor being a sinteredcomposition of claim
 32. .Iaddend. .Iadd.65. A film resistor adherent toa dielectric substrate wherein the resistor comprises a conductive phaseof crystalline particles of (1) pyrochlore-related oxides and (2) metaltitanates, each dispersed in a matrix of a lead containing glass, saidresistor being a sintered composition of claim
 33. .Iaddend. .Iadd.66. Afilm resistor adherent to a dielectric substrate wherein the resistorcomprises a conductive phase of crystalline particles of (1)pyrochlore-related oxides and (2) metal titanates, each dispersed in amatrix of a lead containing glass, said resistor being a sinteredcomposition of claim
 45. .Iaddend. .Iadd.67. A film resistor adherent toa dielectric substrate wherein the resistor comprises a conductive phaseof crystalline particles of (1) pyrochlore-related oxides and (2) metaltitanates, each dispersed in a matrix of a lead containing glass, saidresistor being a sintered composition of claim
 46. .Iaddend. .Iadd.68. Afilm resistor adherent to a dielectric substrate wherein the resistorcomprises a conductive phase of crystalline particles of (1)pyrochlore-related oxides and (2) metal titanates, each dispersed in amatrix of a lead containing glass, said resistor being a sinteredcomposition of claim
 47. .Iaddend. .Iadd.69. A film resistor adherent toa dielectric substrate wherein the resistor comprises a conductive phaseof crystalline particles of (1) pyrochlore-related oxides and (2) metaltitanates, each dispersed in a matrix of a lead containing glass, saidresistor being a sintered composition of claim
 48. .Iaddend.